The SPV1050 is an energy harvesting integrated circuit. It allows the use of small solar cells, thermoelectric generators, or other ambient energy converters that produce low voltages to slowly collect enough charge in a battery or other electric storage device to allow the an extremely long term operation of a low-power device.
The SPV1050 energy harvester chip features battery undervoltage and overcharging protections. It stops charging once the end-of-charge (EOC) voltage is reached and disconnects the battery from the load once its voltage reaches the undervoltage protection (UVP). This extends battery life.
The these two thresholds are set by three resistors that form a ladder between the STORE, EOC, UVP, and GND pins. The EOC and UVP pins each compare their voltage to a 1.23V internal bandgap. The UVP pin disconnects STORE from BATT when its voltage reaches VBG
The selection of these three is described in Section 6.1: Battery Charger, pages 13-15 in the SPV1050 datasheet. Given that VBG is 1.23V, the following equations are true: